The Romans also perfected the metallurgical composition, meaning that smaller keys could now be produced. Which led to the introduction of … padlocks!
It does not seem like a big deal today, but it was a huge step from only being able to lock doors to locking whatever you wanted. And carrying it with you! To suit the new fashion of portable security, the Romans produced key rings. In this case actual rings that were worn on their fingers. What a shame that this fashion did not survive the millennia, I’m sure it’s due a come-back!
So the upshot of this very brief excursion is…